1. Field of the Invention
The present invention relates to compounds of the formula: ##STR1## as further defined herein. The compounds are useful as cardiovascular agents. The compounds possess positive ionotropic activity and are especially useful as cardiotonic agents for improving cardiac ejection, particularly in the setting of acute or chronic congestive heart failure
2. Description of the Prior Art
British Patent Application No. GB2186573 and German Patent Application No. DE3703633 relate to purine derivatives possessing cardiotonic and antiarrhythmic activity and having the following formula: ##STR2## wherein R is an optionally substituted diphenylalkyl group. The side chain in the above formula is bonded to a ring nitrogen atom.
U.S. Pat. No. 4,460,586 relates to 3-aminopropoxyaryl derivatives of the formula: ##STR3## These compounds are useful as cardiotonic, antiarrhythmic and .alpha.- and .beta.-adrenoceptor blocking agents. This United States patent is one of a series of patents that have issued claiming various 4-substituted indole derivatives.
U.S. Pat. No. 4,885,300 relates to 4-substituted pyrazolo pyrimidine derivatives of the formula: ##STR4## These compounds are useful as cardiotonic and antiarrhythmic agents.
U.S. Pat. No. 4,876,257 relates to 6-substituted purinyl piperazine derivatives of the formula: ##STR5## These compounds are also useful as cardiotonic and antiarrhythmic agents.